Biodiversity
Gene banks are important because?
they provide a genetic reservoir of the variety of plant life on earth.
Define Osmosis
Osmosis is the passive movement of water molecules from an area of high water concentration (or low solute concentration) to an area of low water concentration (or high solute concentration) across a partially permeable membrane.
Mitochondria are responsible for
Aerobic pathway of cellular respiration
Name two products of photosynthesis that are used in other plant processes
Glucose and Oxygen
In insects Gas exchange occurs through tiny tubes called?
Spiracles
The Numbat (Myrmecobius fasciatus), a small marsupial with an adult weight between 500 and 700g, once lived across southern and central Australia. The species has suffered a considerable decline. The small natural populations remain, both in Western Australia, with one at Perup and the other at Dryandra. Currently, it is estimated that fewer than 1000 Numbats remain in the wild.
List four Factors that may have led to the decline.
Any Four
- loss of haitat
- degregation in quality of habitat
- predation by introduced species (foxes and Cats)
- disease
- competition
Explain Activation Energy
Activation energy is the minimum amount of energy required for a chemical reaction to occur. (1 mark)
It is needed to break bonds in reactants so that new products can form. (1 mark)
What is the balanced chemical equation for cellular respiration
C6H12O6 + 6O2 --> 6CO2 + 6H2O + Energy
Plant root hairs are very important in the uptake of water from the soil for use in plants. Explain the shape of root hair cells in maximising the uptake of water from the cell
- root hairs increase the SA:V of the cell in contact with the soil
- to increase the uptake of water.
the circulatory system in insects is not involved in Gas exchange explain why.
insects have a separate system of tracheal tubes that provides for gas exchange with cells.
Pesticides are often used in the Wheatbelt of australia on barley and wheat to control insects.
Explain why Eagles and Hawks show greater effects of pesticide poisoning even when they are not present when the spraying occurs.
- Pesticides accumulate in the tissues of the organisms that ingest it/ not eliminated from the body.
- higher order consumers eat prey with greater concentrations of pesticdes in their tissues as it accumulates up the food chain in BIOMAGNIFICATION
- Eagles and Hawks are high order consumers so pesticides accumulate in poisonious levels.
Explain the difference between anaerobic respiration in plants and animals.
Animals: Anaerobic respiration produces lactic acid and a small amount of ATP. (1 mark)
Plants (and yeast): Anaerobic respiration produces ethanol, carbon dioxide, and a small amount of ATP. (1 mark)
Key difference: The end products differ between animals and plants. (1 mark)
explain what would happen if a Plant cell was placed into a Hypotonic solution.
- water would move into the cell through osmosis
- the cell would begin to swell and become turgid
- the cells cell wall would stop it from bursting.
Name and describe the method by which Nitrogen is taken up by plants.
Nitrogen Assimilation
Nitrogen is converted into nitrates
Plant is able to absorb nitrates through root hairs
lipids
proteins
carbohydrates
Small Intestine
Stomach
Mouth
Explain how the Lack of balance in the Carbon Cycle leads to climate change (4 Marks)
- more CO2 going into the atmosphere than is being absorbed by photosynthesis
- the CO2 is a greenhouse gas
- Solar radiation enters the earth atmosphere and warms the earth
- However excess CO2 causes more of the infrared radiation to be trapped, increasing global temperatures.
Explain the difference between the Lock and Key Model and the induced fit model.
Lock and Key model: The substrate fits exactly into the enzyme’s active site, like a key fitting a lock. (1 mark)
Induced Fit model: The enzyme’s active site changes shape slightly to fit the substrate more snugly. (1 mark)
Lock and Key assumes a rigid active site, while Induced Fit accounts for flexibility in the enzyme structure. (1 mark)
Induced Fit is more accurate for most enzymes because it explains how enzymes can stabilise the transition state and increase reaction efficiency. (1 mark)
State the location in a Eucaryotic cell where a biologist would observe the following
1. Deoxyribonucleic acid
2. protein molecules
3. Starch grains
4. Cellulose molecules
1. nuclueus
2. ribosomes, RER, Golgi, cell membrane
3. Chloroplasts
4. Cell wall
explain the structure of the Phloem.
ieve tube elements are long, cylindrical cells joined end to end, with perforated sieve plates between them to allow movement of substances. (1 mark)
Companion cells lie beside sieve tube elements and contain a nucleus and organelles to help control and maintain sieve tube function. (1 mark)
Phloem parenchyma stores nutrients and assists in lateral transport. (1 mark)
Phloem fibres (sclerenchyma) provide structural support to the tissue. (1 mark)
Explain the differnces in carnivore and herbivore digestive systems
Carnivores eat meat, which is easy to digest, so they have a shorter digestive tract; herbivores eat plant material, which is harder to digest, so they have a longer digestive tract to allow more time for breakdown. (1 mark)
Herbivores often have specialised stomachs (e.g. multi-chambered in ruminants) or a large caecum for fermenting cellulose; carnivores have a simple stomach. (1 mark)
Herbivores rely on microorganisms to help digest cellulose; carnivores rely mainly on enzymes to digest proteins and fats. (1 mark)
Teeth differ: herbivores have broad, flat molars for grinding plant matter, while carnivores have sharp canines and incisors for tearing flesh. (1 mark)
Explain why food chains are rarely longer than 4 trophic levels.
- in a food chain only 10% of the available energy is available to the next level.
- this is because mch of the energy consumed by a animal is used up by biochemical processes or stored in undigestible components eg bones.
- as you move up a food chain the available energy to pass on becomes smaller with each level
- high order consumers at trophic levels 4 and above would have to consume huge amounts of prey to sustain life
- thus food chains tend to be only 4 trophic levels high.
Describe the structure of the cell membrane
he cell membrane is composed of a phospholipid bilayer, with hydrophilic (water-attracting) heads facing outwards and hydrophobic (water-repelling) tails facing inwards. (1 mark)
Proteins are embedded within the bilayer, including integral proteins (span the membrane) and peripheral proteins (on the surface). (1 mark)
Carbohydrates are attached to proteins (glycoproteins) or lipids (glycolipids) and are involved in cell recognition and signaling. (1 mark)
The membrane is semi-permeable, allowing selective movement of substances in and out of the cell. (1 mark)
Cholesterol molecules are interspersed within the bilayer, providing stability and fluidity to the membrane. (1 mark)
describe the differences between Prokaryotic and Eukaryotic cells.
-Eukaryotes have a true nucleus where prokaryotes have DNA floating in the cytoplasm
- eukaryotes have membrane bound organelles and prokaryotes dont
- Eukaryotes are generally larger than prokaryotic cells
- some prokaryotic cells have pili and flagellum while eukaryotic cells done.
eg prokaryotic bacteria cell
eg eukaryotic plant cell
Explain the process of gas exchange in plants
Gas exchange in plants occurs mainly through stomata on the surfaces of leaves. (1 mark)
Carbon dioxide (CO₂) diffuses into the leaf through open stomata for use in photosynthesis. (1 mark)
Oxygen (O₂), produced as a by-product of photosynthesis, diffuses out of the leaf through the same openings. (1 mark)
Diffusion drives the movement of gases along their concentration gradients between the air and the intercellular air spaces within the leaf. (1 mark)
Guard cells control the opening and closing of stomata to regulate gas exchange and water loss through transpiration. (1 mark)
Explain how Gas Exchange in fish is efficient.
Fish gills have a large surface area due to gill filaments and lamellae, which increases the area for oxygen diffusion. (1 mark)
Thin, moist surfaces of gills allow gases to diffuse easily between water and blood. (1 mark)
The counter-current flow system means water and blood flow in opposite directions, maintaining a high concentration gradient for oxygen across the gill surface. (1 mark)
This system allows fish to extract up to 80–90% of oxygen from water, which is much more efficient than if blood and water flowed in the same direction. (1 mark)